The present invention relates to a closing member for compressed air carrying polygonal tubes of the type used as a mounting rod for the drafting system in a yarn spinning machine.
In such spinning machines, pneumatically loadable top roller support and weighting arms are used, which are secured by means of brackets to a mounting rod of the machine. The mounting rod is hollow and serves at the same time as a compressed air delivery line. A drafting system of this type is described, for example, in DE 198 29 403 A1.
DE 198 30 048 A1 discloses a mounting rod that is formed from polygonal tube sections, with each tube section being provided at its ends with closing members. A mounting rod that is composed of individual tube sections permits a modular construction of the mounting rod and compressed air supply for spinning machines of different lengths. The closing members are inserted in a sealing manner into the ends of the polygonal tube sections. Between the polygonal tube sections, the compressed air is conducted through a connecting tube section which interconnects the closing members of two adjacent sections.
Sealing of non-circular hollow sections with elastic sealing elements, such as O-rings with a circular cross section, or with special section rings, presents problems, inasmuch as irregularities of the special section of the sealing element causes in the latter only a certain equalization of internal tension, without the sealing element filling all zones of the hollow section in a uniform and sealing manner. It is therefore preferred to use in the case of polygonal hollow sections, pasty sealing substances of a suitable viscosity, which must completely fill a sealing channel that is formed by the hollow section and an inserted sealing element. It is however difficult to fill the sealing channel evenly and completely, as well as in a process safe manner in the case of series production. This requires a great expenditure for production and testing. The sealing effect is often not stable for a long duration because of the aging behavior of the sealing substance and because of operational stress, for example, as a result of pressure changes. Thus a reliable, lasting sealing is not ensured.
If leakages occur in operation, sealing elements of the described type are hard to disassemble and cannot be reused. It is therefore often necessary to exchange the entire special section tube length. Likewise, the sealing substance is able to only a very limited extent retain the sealing element in the required position against the inner pressure in the special section tube. This requires additional special measures, for example, the installation of pins for securing the sealing element against axial displacement.
If an adhesive is used as sealing substance to increase the hold of the sealing element in its position at the end of the polygonal tube, it will be difficult and costly to disassemble the closing member. In this case, the closing members and, possibly, even the polygonal tube will no longer be suited for immediate reuse.
At their ends, the polygonal tubes are supported in recesses of brackets that are also known as stands, and secured in position by means of screw connections. To this end, a mounting screw extends through the special-section tube in its end region, which also mounts the respective closing member. By tightening the mounting screw, the polygonal hollow section may undergo elastic or plastic deformations, whereby the sealing effect is additionally put at risk.
Based on the foregoing state of the art, it is an object of the invention to overcome the above limitations and deficiencies of the known closing members.